Binding of Polyatomic Anions with Protonated Ureido-pyridyl Ligands

Abstract

Two ureido-pyridyl ligands, 1-(4-nitro-phenyl)-3-pyridine-3-ylmethyl-urea (L1) and 1-pentafluorophenyl-3-pyridine-4-yl-urea (L2) were synthesized in good yields, and solid-state anion binding studies of (HL1)+ and (HL2)+ with polyatomic anions such as NO3−, AcO−, ClO4−, SO42−, and SiF62− were carried out in detail. Protonation of the pyridyl nitrogen center of L1 with HNO3, HClO4, and HF in different solvent media yielded crystals of complexes 1 (HL1·NO3), 2 (HL1·ClO4), and 3 (HL1·0.5SiF6) suitable for single crystal X-ray diffraction studies, respectively. Similarly, protonation of L2 with HNO3, CH3COOH, and H2SO4 yielded single crystals of complexes 4 [2(HL2·NO3)·DMF], 5 (HL2·AcO), and 6 [(HL2)2·SO4], respectively. X-ray crystallographic analysis of all these six complexes has been carried out and the details of anion binding with the urea functionality of ureido-pyridyl ligands were investigated. In all the complexes, the pyridyl moiety of the ligands is found to be protonated and the binding of anions...